Process of producing ferrophosphorus in rotary furnaces.



- tary Furnaces; and

hurrah STATES PATENT onnion.

EYLEMAN ALISQN WEBSTER, 0F COLUMBIA, TENNESSEE, ASSIGNOB TO JOHN J.GRAY, JB., 0F BOCKDALE, TENNESSEE.

'EROCEFS OF FBEtGDUCING FERR-OPHOSPHORUS IN ROTARY FURNACES.

it .2 same.

2'70 marr ing.

To all whom it may concern:

Be it known that I, ll'lYLIJMAN ALISON l'vnnsrnn, a citizen of theUnited States, residin at Columbia, in the county of Maury and tate ofTennessee, have invented certain new and useful Improven'icnts inProcasses of Producing Fcrrophosphorus in R0- 1 do hereby declare thefollowing to be a full, clear, and exact de- ,scription of theinvention, such as will enable others skilled in the art to which itappcrtains to make and use the same.

T his invention relates to a process of producing ferro-phosphorus fromphosp ate rock in a rotary kiln furnace, and has for its object toprovide a method which will be eflicient in action, continuous inoperation, and less costly to carry out than those heretofore proposed.

With these and other objects in view the invention consists in the novelsteps and ci'mibinations of steps constituting the invention, all aswill be more fully hereinafter I disclosed and particularly pointed outin the claims.

In the'prior U. S. Patent #831427, issued to John J. Gray, Jr., anddated September 18, 1906, entitled Manufacture of ferro'phosphorus thereis disclosed a blast furnace process of producing ferro-phosphorus fromtri-calcium phosphate, but in such process the ore of necessity has tobe of a size suitable for blastfurnace practice, and it results amongother things that such an intimate contact between the carbon and ore isnot had as is the case in a rotary kiln furpace where theore can be morefinely subdivided and the carbon can be more thoroughly mixedthercwith.In addition to the above, in a process of producin ferro-phosphorus fromphosphate rock, it is very desirable indeed to control the temperatureas accurately as possible in the fusion zone so as o more eliicientlyreduce the phosphorus n'hne in contact with incandescent carbon, andthereby avoid anv phosphorus going to Waste, The rotary, kiln furnacelends itself to this desirable result better than a blast furnace inthat the heat can be supplied from an oil blast burner, a blast fed byproducer gas or by other Well known fuels, and therefore; can becontrolled to a much more accurate degree than is possible in a blastfurnace, In addition, substantially the en- Specification of LettersPatent.

phorus in a blast furnace,

Patented May '7, 1918.

Application filed October 13, 1916. Serial in. 125,409.

tire interior of the rotary furnace may be made to serve as a. zone ofincandescent car-- bon or a reduction zone for the phosphorus, so thatthe said phosphorus has practically no chance to escape unreduced, thus'roducing more favorable conditions for tie purpose in hand than ispossible in a blast furnace.

The above features are of peculiar importance in the production of highgrade ferrophosphorus containing above say 15% or 20% of phosphorus asWill fully explained.

In the making of high rade, ferro-phosimpossible to get as intimate amixture of the carbon and rock material as is desired because theoperator is limited in the finencss to which the material can be usedinthe furnace. This results in a less cflicient reduction of thephosphorus and also a higher fuel cost than is desired. In the rotarytype of furnace, on the other hand, no such objections are met with. Andin addition to this, the chemical principles underlying the successfulcommercial production of high grade form-phosphorus peculiarly combinewith these advantages as will now more fully appear.

now be more it is substantially I That is to say, it is not generallyknown that carbon monoixid CO, under the increas- IIIg'PIQSSUI'QS thatexlst in a blast furnace,

will not reduce oxide of phosphorus such as P 0 to the elemental state;althoughunder atmospheric pressure it Will reduce P 0 to lower oxids ofphosphorus.

In other Words, it is not generally known that in making the above highgrade ferrophosphorus in a blast furnace, it is impracticable to utilizethe CO present to reduce the phosphorus. On the other hand, no suchincreasing pressures are met with in a rotary furnace, butonlysubstantially normal pressures, and therefore, I can rely on the COgenerated in the rotary furnace to partially reduce the P 0 to theelemental state, and

' can therefore effect a. material saving in fuel.

ther evident that if any unreduced phosphorus escapes from this zone itis lost to the product. But the extent of this zone is limiii ited in ablast furnace. and therefore such limitation requires an abnormalquantity of carbon to be employed in a blast furnace to obtain therequired amount of elemental phosphonis. in the rotary furnace, on theother hand, no such limitation of the 1ncandescent zone is met with andshould some phosphorus'escape unrerluced from one part of the furnace,it will pass on only to meet with incandescent carbon and suil'erreduction inanother portion of the furnace.

Again the finer sub-division of the charge in a rotary furnace and theresulting more intimate contact of the constituents greatly aid inbringing about the desired reactions and a further saving of fuel isattained.

Accordingly, in carrying out this process I provide any suitable rotarykiln furnace and I prepare a suitable charge of phosphate rock such astricalcium phosplmte and mix therewith a quantity of carbon which whenadded to the'carbon carried by the fuel blast will he in excess of thatrequired to reduce all the combined phosphorus present to an elementalstate. I also add a-slight excess of silica over that necessarytocompletely satisfy the calcium oxid and other bases present. I crush thecharge thus prepared to a suitable state of line subdivision say to aquarter inch mesh or even finer, and I continuously charge this mixtureinto the rotating furnace.

omitting the air and not counting the carbon introduced by the blast,the following may be considered as an example of the proportions of{charge that would be suitable mcarrymg out this process Lbs. Tri-calcium phosphate, C21,,

2 8 1050 Calcium fluorid, CaFl Calcium carbonate, CaCO 224 Calciumsulfate, CaSO Silica, SiQ 63 Iron ore Fe O 63 Total phosphate rock 1400Fol) 700 so 252 Al plus H 9 w 4 8 Total iron ore i400 Silica, .,and orflint:

K 0 (it- Total J 64.0 Coke as carbon, C 1000 The amount of airrcquircdin any given case will depend upon the quantity of mate: rials charged,upon the speed of rotation of the furnace and u pen the temperaturemaintained inside the furnace. The cxactproportions will be determinedby the furmwe on, when it is desired to reach a i'uaximuzto capacity asfollows:

Suppose the fuel blast is in) set tain a given temperature oi i on theinside of the furnace, the ope will pass in the above mixture atdetermined speed and admit a gi of air into the furnace whereupon in:will rotate the furnace at diilcrcnt lum ls i.

watch the materials at the furnai t a they show a satisfactory reactionbotto -n the constituents of the charge. lihen this condition. has beenattained the furnace will probably not be operating at i maximum socapacity and the furnace man will. next increase the speed of feed ofthe material and at the same time increase the air blast, le ing thespeed of rotation and the fuel blast constant and when the properreaction has so again been reached the speed of rolion. is againincreased as Well as the quantity of charge material and so on, untilthe maximum capacity of furnace is attained.

The heat may be conveniently supplied to p the furnace as above statedby any suitaltlle blast and it is under absolute control the temperatureinside the furnace is gtn'erncd to such a nicety that a uniform productis easily produced ditions.

The reduced iron is obtained in a relatively fine state of sub-division,it readiy takes up the liberated phosphorus, and a high grade off8H'Q-PiIOSPhOXUS in the town of nodules results at once. The slag, onother hand, separates to a. greater or 5x tent from the ferrophosphorusthus formed, and'the whole mass passes out the exit earl of the furnacewhere it may be received in it Water and the slag granulated.

After the slag has been thus sub-divided the mass of granular slag andnodular ferrophosphorus is passed through any suitable magnetic or otherseparator and the ferro- ,1. phosphorus recovered. i

In this process the acids and oases are carefully balanced. or leg y 31parts silica Sit), to each part of caleuin oaicl Cat). or magnesiumoxid. ldgt), when the latter is present. In using such an excess ofsilica in the charge when proper temperatures are reached, say 1100 C,to 600" (1., the SiQ ettaeks the tri-calcium phosphate of the charge,combines with the calcium oxid, or map; nesium oxiclif present, to formcalcium silicate CaSiO or magnesium silicate MgSiO.. and liberatesphosphorus pentoizid 1 0;, while the incandescent carbon presentimmediately deoxidizes the P 0 to elemental phosphorus P It is obviousthat those skilled in the art. may vary the details of the processwithout departing from the spirit of-the inv *o:a, apd therefore, I donot wish to be limited ilii messes the ehore disclosure except, as maybe required by the claims.

What I claim is The process of producing form-phospligylrus in a rotaryfurnace containing above 3 .010 phosphorus from phosphate rock whichconsists in charging into said furnace a suitable mixture of sub-dividedphosphate rock, silice in excess and carbon bjcctim said mixture to theaction. of to tem @erature above'1000 C. and (i, revolving the furnacein order to bring about an intimate contact of its oonstituer f s;mainmining incandescent carbon throughout the charge collecting theferro'phosphorus and slag thus produced; and suitably recovering saidferro-phosphorus, substznitially as described.

12. The process of producing ferro-phosphorus in a rotary furnacecontaining above 10% phosphorus from phosphate rock which consists incharging into said furnace a suitable mixture of subdivided phosphaterock, silica in excess and carbon; said carbon be .ing in of thatrequired to reduce the phosphorus present to an elemental. state;subjecting said mixture to the action. of a r and to a temperature above1000 Ci 2;

below 1"2'50 (l; continuously maintaining incandescent carbon throughoutthe charge while revolving the furnace in order to bring about anintimate contact of its constituents; collecting the form-phosphorus andslag thus produced; and suitably recovering said fare-phosphorussubstantially as described.

3. The process or" producing ferro-phosphorus ine rotary furnacecontaining above 10% phosphorus from phosphate rock which consists incharging into said furnace a suitable mixture of sub-divided phosphaterock, silica, and carbon; said carbon being in cx cess' of that requiredto reduce the phosphorus present to the elemental state and said silicabeing in excess of that necessary to satisfy the bases present;subjecting said mixture to the action of air and to a temper ature above1000 (1, maintaining incandescent carbon throughout the charge Whilerevolving the same in order to bring about an intimate contact of itsconstituents; collect ing said form-phosphorus and slag thus pro-vduced; and suitably recovering said ferro- 11;hos horus, substantiallyas described.

in testimony whereof I aflix my signature iii-presence of e Witness.

HYLEMAN ALISON WEBSTER.

